Effects of physical training on the ventilatory response to exercise in patients on chronic hemodialysis

Abstract

This study examined the effects of physical training on exercise hyperpnea (EH) in patients on hemodialysis (HD). In baseline, 17 (trained group) and 12 (control group) patients on HD performed symptom limited exercise test using a treadmill. Trained group, but not control group, exercised 2 to 3 times weekly on non-dialysis days under medical supervision. Exercise testing was repeated 20 weeks after the baseline. Ventilatory response to exercise was evaluated using the regression slope relating minute ventilation (V̇E) to carbon dioxide output (V̇CO2) during incremental exercise (V̇E/V̇CO2 slope) below the point of respiratory compensation. In trained group, V̇E, oxygen uptake (V̇O2) and V̇CO2 at peak exercise increased and V̇E/V̇O2 and V̇E/V̇CO2 decreased after physical training, respectively. No change was observed in control group. V̇O2 at the anaerobic threshold increased in trained group, but not in control group. The post training V̇E/V̇CO2 slope (33.9±5.0) was significantly (p<0.05) lower than the pre-training slope (38.0± 4.8) and remained constant in control group. In trained group, changes in the V̇E/V̇CO2 slope correlated with those in peak V̇O2 (p<0.05). These results suggest that physical training decreases EH in patients on HD and that it correlates with changes in exercise tolerance.